In order to improve the mechanical and ablative resistance of c/ccomposites, (Hf-Ta-Zr)c single-phase solid solution ceramics were introduced into c/ccomposites by polymer infiltration and pyrolysis (PIP) to fabrica...
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In order to improve the mechanical and ablative resistance of c/ccomposites, (Hf-Ta-Zr)c single-phase solid solution ceramics were introduced into c/ccomposites by polymer infiltration and pyrolysis (PIP) to fabricate (Hf-Ta-Zr)c modified c/ccomposites (HTZ). Their mechanical property and ablation resistance were studied. The results showed that HTZ achieved simultaneous enhancement of mechanical property and ablative resis-tance. Their flexural strength and modulus could reach 219.34 MPa and 24.82 GPa, respectively. In addition, the mass and linear ablation rate of HTZ were 0.379 mg/s and 0.667 mu m/s, respectively after the 90 s oxyacetylene ablation. A dense Hf-Ta-Zr-O multiphase oxide layer was formed on the surface of the HTZ during ablation process, which protected the interior modified c/ccomposites from ablation. Our work expands a rational design of modified c/ccomposites and broaden the application of solid solution ceramic in the field of ultra-high temperature ablation resistance for carbon or ceramic-based composites.
Single-particle imaging using laser-illuminated widefield epi-fluorescence microscopy is a powerful tool to investigate molecular processes in vivo. Performing high-quality single-molecule imaging in such biological s...
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Single-particle imaging using laser-illuminated widefield epi-fluorescence microscopy is a powerful tool to investigate molecular processes in vivo. Performing high-quality single-molecule imaging in such biological systems, however, remains a challenge due to difficulties in controlling the number of fluorescing molecules, photobleaching, and the autofluorescence background. Here, we show that by exciting only a small, 5-15 & mu;m wide region in chemosensory neurons in live c. elegans, we can significantly improve the duration and quality of single-molecule imaging. Small-window illumination microscopy (SWIM) allows long-duration single-particle imaging since fluorescently labelled proteins are only excited upon entering the small excited area, limiting their photobleaching. Remarkably, we also find that using a small excitation window significantly improves the signal-to-background ratio of individual particles. With the help of theoretical calculations, we explain that the improved signal-to-background ratio is due to reduced background, mostly caused by out-of-focus autofluorescence. We demonstrate the potential of this approach by studying the dendritic transport of a ciliary calcium channel protein, OcR-2, in the chemosensory neurons of c. elegans. We reveal that OcR-2-associated vesicles are continuously transported back and forth along the length of the dendrite and can switch between directed and diffusive states. Furthermore, we perform single-particle tracking of OcR-2-associated vesicles to quantitatively characterize the transport dynamics. SWIM can be readily applied to other in vivo systems where intracellular transport or cytoskeletal dynamics occur in elongated protrusions, such as axons, dendrites, cilia, microvilli and extensions of fibroblasts.
c/c-BN composites containing different contents of h-BN particles were prepared by chemical vapor infiltration (cVI), presenting different microstructures and pyrolyticcarbon (Pyc) textures. The effects of different ...
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c/c-BN composites containing different contents of h-BN particles were prepared by chemical vapor infiltration (cVI), presenting different microstructures and pyrolyticcarbon (Pyc) textures. The effects of different micro-structures and Pyc textures on the thermo-physical properties and their phonon mechanisms at 30-900 degrees c were investigated. The temperature dependence of heat capacity follows Debye's phonon theory, especially in the low -temperature section (30-300 degrees c) and the temperature dependence of thermal conductivity is determined by heat capacity and mean free length of phonon. Due to the higher texture of h-BN and regenerative laminar Pyc (ReL-Pyc), h-BN addition causes higher Debye temperature (Theta D) and high sensitivity of thermal conductivity to temperature. Besides, h-BN addition significantly changes the microstructure of composites such as pore struc-ture, Pyc morphology, crack distribution and fiber/Pyc interface bonding state, causing the transformation of thermal conductivity from anisotropy to isotropy. Finally, based on the different microstructures of composites, the microstructure model and thermal resistance formulas of composites were established and coincident with the experimental results.
continuous and pulsed inputs of labile organiccarbon (LOc) into soil are common. However, because soil mi-crobial responses to LOc input are rapid, the relative contributions of respiration derived from LOc to total ...
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continuous and pulsed inputs of labile organiccarbon (LOc) into soil are common. However, because soil mi-crobial responses to LOc input are rapid, the relative contributions of respiration derived from LOc to total microbial respiration and their influencing factors remain elusive. Furthermore, although numerous studies have explored the priming effect (PE) of soil organic matter (SOM) mineralization induced by LOc addition, few studies have focused on its short-term effects. There are some indications that the response of soil microbes to LOc input depends on the microbial demand of nutrients, especially c and N. Therefore, variations in soil c and N characteristics may further influence microbial response processes to LOc inputs and the decomposition of LOc and SOM, but a comprehensive understanding of this is lacking. To address this gap, 13c-labeled glucose was added to six temperate grassland soils with different c/N ratios (9.98-12.0), which were collected from areas with different grazing exclusion durations and at different soil depths. The microbial respiration was measured at 9-min intervals across a 105-h period. We found that soil microbes responded rapidly to LOc input, and mi-crobial biomass controlled by soil organicc (SOc) and c/N was the most important factor directly influencing the intensity of the microbial response to LOc input. Grazing and deeper soil layers decreased the respiration derived from LOc and their relative contribution to total respiration, mainly attributed to variations in soil c/N and fungal/bacterial ratio (Fu/Ba). LOc addition stimulated SOM decomposition in all soils and increased respiration of SOM by 11.3-92.4 mg c/g SOc, equivalent to 18.7-266.1 % priming. Grazing and increased soil depth resulted in a greater PE and soil c loss, with soil c/N and SOccontent being the most important regulators. Overall, this study revealed the important influence of LOc on soil c fluxes and highlighted the important role of SOM quality
To maintain the thermal stability of Sic nanowires during Siccoating fabrication process, carbon and Sic double protective layers were covered on the surface of nanowires. And Sic nanowires with double protective lay...
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To maintain the thermal stability of Sic nanowires during Siccoating fabrication process, carbon and Sic double protective layers were covered on the surface of nanowires. And Sic nanowires with double protective layers toughened Siccoating were prepared by pack cementation. The results showed that after introducing the Sic nanowires with double protective layers, the fracture toughness of the Siccoating was increased by 88.4 %. The coating protected c/c for 175 h with a mass loss of 3.67 %, and after 51 thermal shock cycles, the mass losses of the oxidized coating were 3.96 %. The double protective layers are beneficial to improve the thermal stability of nanowires, leading to good fracture toughness and thermal shock resistance of Siccoating. Sic nanowires consume the energy of crack propagation by fracture, pullout and bridging, leading to an increase in fracture toughness.
In this study, niobium-based alloy c103 is joined to carbon fibre-reinforced Sic (c/Sic) composite utilising commercially available Ticusil & REG;and cusil & REG;alloy braze filler material. Various characteri...
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In this study, niobium-based alloy c103 is joined to carbon fibre-reinforced Sic (c/Sic) composite utilising commercially available Ticusil & REG;and cusil & REG;alloy braze filler material. Various characterisation techniques are employed to investigate the interfacial microstructures and evolution mechanism of c/Sic-c103 junctions. Lap shear strength (LSS) is used to evaluate the mechanical performance of the brazed joints. The results show that adding Ti promotes the growth of "nails", a phenomenon favourable for robust joint quality. However, high Ti content deteriorates the bond strength due to the formation of significant brittle intermetallic phases, causing premature delamination of the joints. The response surface methodology (RSM) is employed to examine the interactions among various operating parameters. To attain the high LSS value, the high temperature, intermediate reaction time, and low cooling rate are necessary for a Ticusil-based joint, whereas high temperature, low reaction time, and increased cooling rate are preferred for a cusil-based joint.
The multi-directional laminate ccF800H/Ac631 bismaleimide composite material was exposed for a long time under the thermal-cycling environment (-60 degrees c similar to+180 degrees c), and the mass loss rate, FTIR spe...
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The multi-directional laminate ccF800H/Ac631 bismaleimide composite material was exposed for a long time under the thermal-cycling environment (-60 degrees c similar to+180 degrees c), and the mass loss rate, FTIR spectra, DMA, tensile strength were tested. The fatigue stress level was determined according to the tensile strength and the fatigue performance of the before and after the thermal-cycling environment was tested. Macroscopic visual inspection and ultrasonicc-scan were used to characterize and analyze the fatigue damage of composite materials. The results show that with the increase in the number of thermal cycles, the mass loss of the composite material started with increased rapidly and then basically flat. The c/BMI composites underwent obvious thermal oxygen aging. After thermal-cycling, it would lead to changes in dynamic mechanical properties by a certain degree of post-curing, physical aging, and local interface debonding in composite materials. With the thermal cycles increased the composite material tensile strength first increased slightly and then decreased rapidly. After 300 thermal cycles, the composite materials occurred slightly damaged, and the fatigue life was apparently reduced compared with the original state. The fatigue failure modes of composite materials are mainly fiber fracture and multi-directional laminate delamination. At high stress levels, the stiffness of the specimen after thermal-cycling are lower decrease compared with original specimens, more stress levels would lead to more II stage rate of stiffness decline, and stiffness degradation curve and hysteretic energy recovery curve had enough effect to characterize damage effect of material environment induced by thermal-cycling environment factors.
A new organic silicone composite coating modified by Al, ZrO2, quartz and PbO-SiO2-Al2O3 glass powders was developed to protect Ti-6Al-4V alloy. During oxidation at 600 degrees c in dry air, the coating was oxidized a...
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A new organic silicone composite coating modified by Al, ZrO2, quartz and PbO-SiO2-Al2O3 glass powders was developed to protect Ti-6Al-4V alloy. During oxidation at 600 degrees c in dry air, the coating was oxidized and formed an inorganiccomposite coating composed of amorphous silica framework and fillers which greatly decreased oxidation rate of substrate. Al2SiO5 formed in coating due to reaction of Al with glass. Glass powders with softening point of 385 degrees c may play important roles in improving coating protectiveness because they can flow to fill the cavities formed by oxidation of organiccomponents in coating at 600 degrees c.
作者：
chatterjee, SubhasishKean Univ
Dorothy & George Hennings Coll Sci Math & Technol Dept Chem & Phys Union NJ 07083 USA
Diamond nanoparticles represent an elegant class of nanoscale materials with promising applications in nanotechnology. Solid-state NMR is a powerful technique for investigating the atomic-level structure and dynamics ...
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Diamond nanoparticles represent an elegant class of nanoscale materials with promising applications in nanotechnology. Solid-state NMR is a powerful technique for investigating the atomic-level structure and dynamics of nanomaterials in their natural state. The present study illustrates the application of high-resolution c-13 NMR to nanomaterials characterization, and the fundamental c-13 spin-lattice relaxation times highlight the spatial arrangement of surface-associated paramagneticcenters around the core sp3 carbon assembly of diamond nanoparticles, delineating the unique size-dependent physicochemical characteristics of diamond nanoparticles.
The tubular microsphere structure is an effective structure for asymmetric supercapacitors due to its high specific surface area and porosity. It can slow down the volume shrinkage caused by redox process. In this pap...
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The tubular microsphere structure is an effective structure for asymmetric supercapacitors due to its high specific surface area and porosity. It can slow down the volume shrinkage caused by redox process. In this paper, tubular -like NiMoO4 center dot xH2O microspheres were designed to reach a high specificcapacity. The NiMoO4 center dot xH2O was pre-pared by hydrothermal method and subsequent annealing treatment showed a tubular microsphere structure with many particles uniformly distributed. And its specificcapacity is 943 F g-1 at 1 A center dot g- 1 and capacity retention is 73.4 % after 3000 cycles. The Bi2S3/c was selected as negative material to build an asymmetric supercapacitor (battery-type device). It exhibited an impressive specificcapacity (419 F g-1 at 1 A g-1). It was worth noting that the battery-type devices built with NiMoO4 center dot xH2O and Bi2S3/ccan achieve a specific energy of 27.1 Wh kg- 1 at 2456.9 W kg- 1 and capacity retention of 69.2 % after 5000 cycles. It was shown that NiMoO4-xH2O and Bi2S3/c as electrode materials have great potential and can enhance the energy storage application of supercapacitors.
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